The present invention relates to a chainless driving device of a bicycle, which can be assembled easily and operated with a transmission stability.
As shown in FIGS. 1 and 2, front portion of a prior art combination chainless driving device of a bicycle, as disclosed in the Taiwanese Patent 163732, comprises a crank shaft 5A which is driven by a pedal and is housed securely in a crank hanger 62A with a shaft tube 6A fastened thereto. The shaft tube 6A receives therein an inner lining shaft 61A. A sector wheel 3A is fastened securely to an end of the inner lining shaft 61A, which is adjacent to the crank shaft 5A. The sector wheel 3A is provided with a coupling edge 31A engageable with a sector wheel 4A of the crank shaft 5A. A locating mount 1A is provided with a ball slot 11A opposite in location to the coupling edge 31A and with a ball ring surface 12A. A ball supporting plug 2A is disposed in a location corresponding to the ball ring surface 12A and is provided with a supporting edge 21A. The sector wheel 3A, the locating mount 1A and the ball supporting plug 2A are fastened to the inner lining shaft 61A. The ball 14A is arranged between the sector wheel 3A and the ball slot 11A. Another ball 14A is arranged between the ball ring surface 12A of the locating mount 1A and the supporting edge 21A of the ball supporting plug 2A. The rear wheel of the bicycle is driven by a rear gear set, which is in turn driven by the inner lining shaft 61A, which is in turn driven by the crank axle 5A.
The rear wheel of the bicycle is driven by the inner lining shaft 61A which in turn is driven by the sector wheel 3A engaging with the sector wheel 4A of the crank axle 5A. The process of locating the sector wheel 3A on the inner lining shaft 6A is complicated and can not be done easily, unless the component parts used in locating the sector wheel 3A are made in accordance with certain specifications. In addition, the crank hanger 62A must be welded to the bicycle frame with precision, thereby undermining the work efficiency of assembling the driving device of the bicycle.
The rear section of a prior art chainless driving device of bicycle is disclosed in the Taiwanese Patent 154043. The prior art driving device comprises a sector helical gear 9, which is mounted in a gear box 7A in a manner that it engages a sector helical auxiliary gear 100A having a restraining flange 101A. Located in the tubular body of a one-way ratchet sleeve 82A are a steel ball slot 102A, a one-way ratchet 103A, and a double-stepped steel ball slot 104A. A locking plug ring 108A is fastened to a threaded portion 109A. The one-way ratchet 103A meshes with the one-way ratchet sleeve 82A. All components of the driving device are fastened to a middle axle 8C by means of a supporting plug ring 110A and a fastening nut 111A. The gear box 7A is provided with a sleeve 72 located at one end thereof and with a side cover 73A located at another end thereof. In addition, the gear box 7A is further provided with a bearing slot 74A, an axial hole 75A, and an axial hole 76A located oppositely to the axial hole 75A and dimensioned to permit the middle axle 8C to pass through. A locating frame 270A is provided with a through hole 271A and is fastened by means of an upper bearing 112A which is mounted in the bearing receiving slot 74A of the gear box 7A, so that the driven sector helical gear 100A engages a driven sector helical gear 9. The middle axle 8C is put through the axial hole 76A and the through hole 271A of the locating frame 270A and is then fastened securely by means of a nut 113A. The rear section of the driving device is driven by the front section of the driving device. In other words, the one-way ratchet sleeve 82A and a wheel drum 85A are driven by the front section of the driving device to drive the rear wheel of the bicycle. Such design of the driving mechanism as described above is costly and time-consuming. In addition, the middle axle 8C is exerted on by the weight of a bicyclist. Located between the driven end of the wheel drum 85A and the stationary middle axle 8C are large steel balls 106A arranged in an annular manner. These large steel balls 106A are supported by the supporting plug ring 110A and are also responsible for stabilizing the transmission of the driven sector auxiliary gear 110A and the driven sector helical gear 9. The moment of force at the supporting plug ring 110A, which supports the large steel balls 106A, is excessive, thereby making the supporting plug ring 110A vulnerable to a shock caused by a force of reverse action of the rear wheel which happens to hit a hole or a pit in the road. Such incident can bring about an irregular transmission or a structural damage to the middle axle 8c.